CN112679888B

CN112679888B - Vinylidene chloride resin preservative film

Info

Publication number: CN112679888B
Application number: CN202011094993.5A
Authority: CN
Inventors: 矶田奈央子; 广崎真司
Original assignee: Asahi Kasei Corp
Current assignee: Asahi Kasei Corp
Priority date: 2019-10-17
Filing date: 2020-10-14
Publication date: 2023-04-07
Anticipated expiration: 2040-10-14
Also published as: JP2021066872A; JP7525360B2; CN112679888A

Abstract

The present invention provides a vinylidene chloride resin preservative film which does not collapse food wrapped therein even when heated in a microwave oven. A vinylidene chloride resin wrap film comprising a vinylidene chloride resin, wherein the ratio of a low-mobility component measured by pulse NMR is 60% or more.

Description

Vinylidene chloride resin preservative film

Technical Field

The present invention relates to a vinylidene chloride resin wrap.

Background

Vinylidene chloride resins are used for wrap films and the like because of their excellent properties such as transparency, water resistance, and gas barrier properties. In recent years, with the spread of microwave ovens, an operation of heating food wrapped in a preservative film in a microwave oven has been carried out. Microwave heating is the cooking of foods in cold or frozen origin by heating them in a microwave oven.

For example, patent document 1 discloses a technique relating to a polyvinylidene chloride resin wrap film which is suppressed in longitudinal tear failure and is excellent in adhesion and transparency.

Patent document 2 discloses a technique relating to a vinylidene chloride resin wrap film which is free from an odor, is suppressed in thermal decomposition during extrusion molding, and is reduced in changes with time in physical properties such as excessive adhesion of the film and a decrease in drawability.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-168750

Patent document 2: japanese patent laid-open No. 2008-74955

Disclosure of Invention

Problems to be solved by the invention

Conventional vinylidene chloride resin wrap films are excellent in adhesion and therefore, they are used for sealing food and heating, but they shrink during heating. In this case, there is a problem that food is collapsed by the shrinkage of the vinylidene chloride resin wrap.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a vinylidene chloride resin wrap film which does not collapse food wrapped therein even when heated in a microwave oven.

Means for solving the problems

The present inventors have conducted extensive studies to solve the above problems, and as a result, have found that a low mobility component ratio of a vinylidene chloride-based resin wrap measured by pulse NMR is 60% or more, whereby a food wrapped in the wrap does not collapse even when heated in a microwave oven.

Namely, the present invention is as follows.

[1]

A vinylidene chloride resin wrap film comprising a vinylidene chloride resin, wherein the low-mobility component ratio measured by pulse NMR is 60% or more.

[2]

The vinylidene chloride-based resin wrap according to the above [1], wherein the vinylidene chloride-based resin contains 72 to 93% of a vinylidene chloride repeating unit.

[3]

The preservative film of vinylidene chloride resin according to the above [1] or [2], wherein the vinylidene chloride resin contains at least one additive selected from the group consisting of a citric acid ester, a dibasic acid ester, an acetylated fatty acid glyceride and an epoxidized vegetable oil, and the total content of the additives is 2 to 8% by weight.

[4]

A vinylidene chloride-based resin wrap according to any one of the above [1] to [3], wherein the vinylidene chloride-based resin has a low-temperature crystallization initiation temperature of more than 60 ℃ as measured by a temperature-modulated differential scanning calorimeter.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a vinylidene chloride resin wrap film can be obtained, in which food wrapped therein does not collapse even when heated in a microwave oven.

Drawings

Fig. 1 is a schematic view of an apparatus used in the film forming process of the present invention.

FIG. 2 shows an example of the mode of use of the film of the present invention.

Detailed Description

Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[ vinylidene chloride resin wrap ]

The vinylidene chloride resin wrap film (hereinafter also simply referred to as "wrap film") of the present embodiment has a low-mobility component ratio of 60% or more as measured by pulse NMR. The vinylidene chloride-based resin wrap of the present embodiment has such a structure, and thus exhibits an effect that the food wrapped therein does not collapse even when heated in a microwave oven. The reason is not clear, but is presumed as follows.

The low mobility component ratio measured by pulse NMR is a portion in which molecules are not easily moved at high temperature, and is a portion in which the vinylidene chloride-based resin wrap is not easily moved (i.e., is not easily shrunk) even when the temperature reaches high temperature. By setting the low motility component ratio to 60% or more, the shrinkage of the vinylidene chloride-based resin wrap film during microwave oven heating is suppressed, and the food wrapped in the wrap film does not collapse even when microwave oven heating is performed. The reason is assumed, but is not limited to this.

< Low temperature crystallization onset temperature >

The low-temperature crystallization initiation temperature of the wrap film of the present embodiment measured by a temperature modulation type Differential Scanning Calorimeter (DSC) is preferably more than 60 ℃. The wrap film thus constituted tends to be capable of further suppressing collapse of the food wrapped therein when subjected to microwave oven heating. The reason is not clear, and is presumed as follows.

The low-temperature crystallization initiation temperature is an index of the crystallinity, and the higher the temperature, the higher the crystallinity is presumed. That is, it is suggested that the low motility component has a high crystal existence rate, and even if the wrap film reaches a high temperature, the low motility component is not easily shrunk further. Therefore, shrinkage of the vinylidene chloride resin wrap film during microwave oven heating is suppressed, and the food wrapped in the wrap film is less likely to collapse even when microwave oven heating is performed. The reason is assumed, but is not limited to this.

The low-temperature crystallization initiation temperature measured by temperature modulated DSC is preferably 61 to 80 ℃, more preferably 63 to 75 ℃, and even more preferably 65 to 70 ℃ from the viewpoints of the resistance to collapse of food contained therein during heating in a microwave oven and the ease of packaging of food.

Here, the low-temperature crystallization onset temperature refers to an extrapolated onset temperature of an exothermic peak due to low-temperature crystallization in a temperature-heat flow curve of an irreversible component obtained by temperature-rise measurement by temperature-modulated DSC (a temperature at an intersection of a line extending a base line on a low-temperature side to a high-temperature side in the temperature-rise measurement and a tangent drawn at a point where a gradient is maximized on a curve on the low-temperature side of a crystallization peak).

Since crystallization occurs in competition with crystal melting in DSC temperature measurement, it is difficult to study the thermal behavior of microcrystals and to distinguish conventional wrap films from wrap films of the present embodiment in the conventional DSC measurement method because the formation and growth of microcrystals counteract heat flow caused by melting. On the other hand, when the temperature-modulated DSC is used, a heat flow of an irreversible component such as crystallization and a reversible component such as crystal melting or glass transition can be separated, and the thermal behavior of the fine crystal can be evaluated.

In order to increase the low-temperature crystallization initiation temperature of the wrap film to more than 60 ℃, for example, the product of the TD stretch ratio and the MD stretch ratio (TD stretch ratio × MD stretch ratio) can be increased, or the temperature during stretching can be decreased, whereby the stress applied during stretching can be increased to promote oriented crystallization.

< pulse NMR >

The low mobility component ratio of the wrap film of the present embodiment measured by pulse NMR is 60% or more. The low-motility component ratio is preferably 60 to 80%, more preferably 63 to 80%, and still more preferably 65 to 75% in view of satisfying both the property of the inner package not to collapse easily during heating in a microwave oven and sufficient flexibility for packaging food.

The high mobility component ratio of the wrap film of the present embodiment measured by pulse NMR is preferably 10% or less. When the ratio of the high-mobility component is 10% or less, the amount of the component which moves at high temperature and the component which accelerates molecular movement are sufficiently small, and therefore the inner package tends to be less likely to collapse during heating in a microwave oven.

The proportion of the high-motility component is preferably 1 to 10%, more preferably 2 to 8%, and further preferably 3 to 6%, from the viewpoints of sufficient adhesion for packaging food and resistance to collapse of the inclusions during microwave oven heating.

Unlike high-resolution NMR which is generally used for the structural determination of organic compounds and the like, pulse NMR is an analytical method which can measure each relaxation time of 1H nuclei associated with molecular mobility in a system and can determine the presence ratio of each kinetic component in the system with high quantitative performance.

In the present embodiment, in obtaining Cs in the plastic wrap: mole fraction of low motility component, cm: molar fraction of intermediate components and Cl: for the mole fraction of the high mobility component, the spin-spin relaxation time T2 of 1H is used.

Specifically, the spin-spin relaxation time T2 of 1H is used. Specifically, the following equation is preferably applied to the Free Induction Decay (FID) signal obtained by measuring the spin-spin relaxation time T2 of 1H, and the application (fitting) is preferably performed by using the linear least squares method. As specific conditions for measuring pulse NMR, conditions described later in examples can be adopted.

[ formula 1]

C _s : of ingredients with low motilityMole fraction

C _m : mole fraction of intermediate component

C _l : mole fraction of highly motile ingredient

T _s : relaxation time of low mobility component

T _m : relaxation time of intermediate component

T _l : relaxation time of highly motile components

Examples of the method of adjusting the low mobility component ratio measured by pulse NMR to 60% or more include a method of adjusting the stress applied during stretching and adjusting the inner diameter of a die gap by adjusting the product of the stretching ratio in the MD direction and the stretching ratio in the TD direction (MD stretching ratio × TD stretching ratio) and the temperature during stretching. The MD stretching magnification is preferably 4 to 9 times, more preferably 5 to 8 times, and further preferably 6 to 8 times. The MD stretching ratio × TD stretching ratio is preferably 19 to 40 times, more preferably 21 to 38 times, still more preferably 22 to 35 times, and particularly preferably 25 to 33 times. The inner diameter of the die gap is preferably 20 to 60mm, more preferably 25 to 50mm, and further preferably 30 to 45mm.

In addition, the low mobility component ratio can be adjusted by adjusting the vinylidene chloride repeating unit of the vinylidene chloride resin. The content of vinylidene chloride repeating units is preferably 72 to 93%, more preferably 75 to 90%.

Further, the low motility component ratio can be adjusted by adjusting the total amount of the plasticizer. The total amount of plasticizer is preferably 2 to 8%, more preferably 3 to 8%.

Examples of the method for adjusting the proportion of the high-mobility component measured by pulse NMR to 10% or less include a method of adjusting the product of the stretch ratio, the temperature during stretching, the vinylidene chloride repeating unit, and the total amount of the plasticizer.

< thickness of cling film >

The thickness of the wrap film of the present embodiment is not particularly limited, but is preferably 6 to 18 μm, and more preferably 9 to 12 μm. When the thickness of the wrap film is 6 μm or more, the tensile strength of the film is high, and the film breakage during use tends to be further suppressed. Further, there is a tendency that a significant decrease in tear strength does not occur, and that the film is less likely to be cracked from the end cut by the cutting blade attached to the package when the film is taken out from the roll and when the film end rewound into the package is unwound. On the other hand, when the thickness of the wrap film is 18 μm or less, the force required for cutting the wrap film by the film cutting blade can be reduced, the cuttability is good, the wrap film is easily adapted to the shape of the container, and the adhesion to the container tends to be improved. That is, the thickness of the wrap is preferably 6 to 18 μm, more preferably 9 to 12 μm, from the viewpoint of the balance among suppression of film breakage failure, cuttability, and adhesiveness.

The thickness of the wrap film can be measured by the method described in the examples described below.

< tear Strength >

The wrap film of the present embodiment preferably has a tear strength in the TD direction of 2.0 to 6.0cN. Here, the TD direction is a direction perpendicular to the direction in which the wrap is drawn out from the roll. The tear strength was measured by the method described in the examples below.

In the wrap film of the present embodiment, by setting the tear strength in the TD direction to 2.0cN or more, it is possible to reduce cracking particularly when the wrap film is taken out from the roll body, and to suppress unexpected cracking failure when the wrap film is used. On the other hand, when the tear strength in the TD direction is 6.0cN or less, the film is likely to be cracked when cut in the TD direction with a serrated blade attached to the package box, and the cuttability tends to be improved. The tear strength in the TD direction is more preferably 2.5 to 4.0cN.

The tear strength in the TD direction of the wrap film of the present embodiment can be adjusted by the composition of the vinylidene chloride resin, the composition of the additive, the stretch ratio and the stretch speed of the film, the thickness of the film, and the like. The tear strength in the TD direction tends to be improved by, for example, reducing the TD stretching ratio to thicken the wrap, and tends to be reduced by increasing the TD stretching ratio to thin the wrap.

< vinylidene chloride resin >

The vinylidene chloride resin wrap of the present embodiment contains a vinylidene chloride resin.

The vinylidene chloride resin used in the present embodiment is not particularly limited as long as it contains a vinylidene chloride repeating unit, and one or two or more kinds of acrylic acid esters such as vinyl chloride, methyl acrylate, and butyl acrylate may be copolymerized in addition to the vinylidene chloride repeating unit; methacrylates such as methyl methacrylate and butyl methacrylate; acrylonitrile; vinyl acetate and the like which are copolymerizable with vinylidene chloride.

The vinylidene chloride resin content in the wrap film of the present embodiment is not particularly limited, but is preferably 89 wt% or more, and more preferably 93 wt% or more. In the case where the amount is within such a range, the film can be prevented from being easily stretched due to the plasticizing effect of the additive or the like, and the cuttability of the film is further improved, which is preferable.

The vinylidene chloride copolymer preferably has a weight average molecular weight (Mw) of 80,000 to 200,000, more preferably 90,000 to 180,000, and still more preferably 100,000 to 170,000. When the weight average molecular weight is 80,000 or more, occurrence of puncture due to the content having a sharp portion tends to be suppressed, and when the weight average molecular weight is 200,000 or less, processability tends to be excellent. The vinylidene chloride resin having a weight average molecular weight within the above range can be obtained by controlling the charging ratio of vinylidene chloride monomer to vinyl chloride monomer, the amount of polymerization initiator, or the polymerization temperature, for example. In the present embodiment, the weight average molecular weight can be determined by gel permeation chromatography (GPC method) using a standard polystyrene calibration curve.

The vinylidene chloride-based resin wrap of the present embodiment may contain various additives as needed in addition to the above vinylidene chloride-based resin, but is not particularly limited. The additives are not particularly limited, and examples thereof include known stabilizers such as epoxidized vegetable oils, and known plasticizers such as citric acid esters and dibasic acid esters.

The method of measuring the content of each component in the wrap film differs depending on the analyte. For example, the reprecipitated filtrate of the wrap film is vacuum-dried and subjected to weight measurement to obtain the content of the vinylidene chloride resin.

On the other hand, the content of the epoxidized vegetable oil can be obtained by H-NMR measurement, for example. A50 mg sample was weighed, dissolved in a deuterated solvent (solvent: deuterated tetrahydrofuran, internal standard: dimethyl terephthalate, capacity: 0.7 ml), and subjected to 400MHz proton NMR (cumulative number: 512 times) measurement. The ratio of the integrated value of 2.23 to 2.33ppm to the integrated value of 8.05 to 8.11ppm was used as an integral ratio, and a quantitative value was calculated by an absolute calibration curve method.

Integral = integral (2.23-2.33 ppm)/integral (8.05-8.11 ppm)

The contents of citric acid ester, dibasic acid ester and acetylated fatty acid glyceride can be determined by extracting the additive from the wrap film at a temperature 5 to 10 degrees lower than the boiling point of the extraction solvent using an organic solvent such as acetone and performing gas chromatography.

< epoxidized vegetable oil >

The vinylidene chloride resin wrap of the present embodiment preferably contains epoxidized vegetable oil from the viewpoint of suppressing the change in color tone of the wrap. The epoxidized vegetable oil also functions as a stabilizer for extrusion processing of vinylidene chloride resin.

The epoxidized vegetable oil is not particularly limited, and an epoxidized vegetable oil produced by epoxidizing an edible oil or fat is generally used. Specific examples thereof include Epoxidized Soybean Oil (ESO) and epoxidized linseed oil.

When the wrap film of the present embodiment contains the epoxidized vegetable oil, the content thereof is not particularly limited, and is preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight, based on the vinylidene chloride resin, from the viewpoints of suppressing a change in color tone of the wrap film, maintaining the odor barrier property, and the like.

The wrap film of the present embodiment preferably contains at least one compound selected from the group consisting of citric acid esters, dibasic acid esters, acetylated fatty acid glycerides, and epoxidized vegetable oils, from the viewpoint of moldability and the like.

< citric acid ester >

The citrate used in the wrap film of the present embodiment is not particularly limited, and examples thereof include triethyl citrate, tributyl citrate, acetyl triethyl citrate, ATBC, acetyl tri-n- (2-ethylhexyl) citrate, and the like. Among these, ATBC is preferable because of its high plasticizing effect on vinylidene chloride resins, its ability to plasticize the resins sufficiently even in a small amount, and its tendency to improve molding processability.

< dibasic acid ester >

The dibasic acid ester contained in the wrap film of the present embodiment is not particularly limited, and examples thereof include adipate systems such as dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, and dioctyl adipate; azelaic acid esters such as di-2-ethylhexyl azelate and octyl azelate; sebacate systems such as dibutyl sebacate (DBS) and di-2-ethylhexyl sebacate; and so on. Among these, DBS is preferred because of its high plasticizing effect on vinylidene chloride resins, its ability to plasticize the resin sufficiently even in a small amount, and its tendency to improve molding processability.

< acetylated fatty acid glyceride >

The acetylated glycerin fatty acid ester contained in the plastic wrap of the present embodiment is not particularly limited, and diacetylated glycerin monolaurate and the like can be given.

The total content of the citric acid ester, dibasic acid ester, acetylated fatty acid glyceride, and epoxidized vegetable oil is not particularly limited, but is preferably 2 to 8 wt%, more preferably 3 to 7 wt%, even more preferably 3 to 5 wt%, and particularly preferably 3.5 to 5 wt% with respect to the vinylidene chloride-based resin. When the total content of the citric acid ester, dibasic acid ester, acetylated fatty acid glyceride, and epoxidized vegetable oil is 2 wt% or more, it is possible to impart more excellent moldability and further suppress shrinkage during microwave oven heating. When the total content is 8 wt% or less, the shrink during microwave oven heating tends to be further suppressed while preventing excessive adhesion of the wrap film when the additive content is high and maintaining the odor barrier property. The reason why the total content affects the shrinkage characteristics during heating in a microwave oven is not clear, and is presumed as follows.

When the total content of the citric acid ester, the dibasic acid ester, the acetylated fatty acid glyceride, and the epoxidized vegetable oil is 2% by weight or more, the mobility of the amorphous component increases, and therefore the ratio of the crystal to the low mobility component increases, and the low mobility component is less likely to shrink. On the other hand, when the total content of the citric acid ester, the dibasic acid ester, the acetylated fatty acid glyceride and the epoxidized vegetable oil is 8 wt% or less, the low exercise component is less likely to shrink because the proportion of the additive contained in the low exercise component decreases. The reason is assumed, but is not limited to this.

< other Compounds >

The vinylidene chloride-based resin wrap of the present embodiment may contain a compound (hereinafter referred to as "other compound") other than the epoxidized vegetable oil, the citric acid ester, the dibasic acid ester and the acetylated fatty acid glyceride, for example, a plasticizer, a stabilizer, a weather resistance improver, a colorant such as a dye or a pigment, an antifogging agent, an antibacterial agent, a lubricant, a nucleating agent, an oligomer such as a polyester, a polymer such as MBS (methyl methacrylate-butadiene-styrene copolymer), and the like.

The plasticizer is not particularly limited, and specific examples thereof include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, glycerin esters, waxes, liquid paraffin, and phosphoric esters.

The stabilizer is not particularly limited, and specific examples thereof include antioxidants such as 2, 5-t-butylhydroquinone, 2, 6-di-t-butyl-p-cresol, 4 '-thiobis (6-t-butylphenol), 2' -methylene-bis (4-methyl-6-t-butylphenol), octadecyl-3- (3 ',5' -di-t-butyl-4 '-hydroxyphenyl) propionate, and 4,4' -thiobis (6-t-butylphenol); thermal stabilizers such as laurate, myristate, palmitate, stearate, isostearate, oleate, ricinoleate, 2-ethylhexyl salt, isodecanoate, neodecanoate, and calcium benzoate.

The weather resistance improver is not particularly limited, and specific examples thereof include ultraviolet absorbers such as ethylene-2-cyano-3, 3' -diphenylacrylate, 2- (2 ' -hydroxy-5 ' -methylphenyl) benzotriazole, 2- (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) 5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone and 2,2' -dihydroxy-4-methoxybenzophenone.

The colorant such as the dye or the pigment is not particularly limited, and specific examples thereof include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, and iron oxide red.

The antifogging agent is not particularly limited, and specific examples thereof include glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene fatty acid alcohol ether, polyoxyethylene glycerin fatty acid ester, and polyoxyethylene sorbitan fatty acid ester.

The antibacterial agent is not particularly limited, and specific examples thereof include silver-based inorganic antibacterial agents.

The lubricant is not particularly limited, and specific examples thereof include fatty acid hydrocarbon-based lubricants such as ethylene bis stearamide, butyl stearate, polyethylene wax, paraffin wax, carnauba wax, myristyl myristate, and stearyl stearate, higher fatty acid lubricants, fatty amide-based lubricants, and fatty acid ester lubricants.

The nucleating agent is not particularly limited, and specific examples thereof include phosphate metal salts.

The content of the other components is preferably 5% by weight or less, more preferably 3% by weight or less, further preferably 1% by weight or less, and particularly preferably 0.1% by weight or less, relative to the wrap film.

[ Process for producing a vinylidene chloride-based resin wrap film ]

The method for producing the vinylidene chloride-based resin wrap film of the present embodiment is not particularly limited, and for example, a method in which a resin composition containing a vinylidene chloride-based resin or the like is melt-extruded and then stretched in the MD direction and the TD direction can be used. In this case, for example, the stretching ratio in the MD may be 4 to 9 times, and the stretching ratio in the TD may be 2 to 6 times.

Next, a preferred method for producing the wrap film of the present embodiment will be described.

First, a vinylidene chloride resin, optionally at least one compound selected from the group consisting of epoxidized vegetable oils, citric acid esters, dibasic acid esters and acetylated fatty acid glycerides, and optionally various additives are uniformly mixed by a ribbon blender, a henschel mixer or the like, and aged for 24 hours to produce a vinylidene chloride resin composition. Thereafter, as shown in a schematic diagram of an example of a process for producing a wrap film in fig. 1, the resin composition is melted by an extruder (1) and extruded in a tubular shape from a die head (2) to form a dip part (4). The outside of the soaking part (4) is brought into contact with cold water in a cold water tank (6), and a soaking solution (5) is injected into the soaking part (4), thereby cooling the inside and the outside and solidifying the inside and the outside. The solidified soaking part (4) is folded by a 1 st pinch roll (7) to form a parison (8).

Then, air is injected into the parison 8 to reopen the parison 8 and form a tube. At this time, the dipping solution (5) which coats the inner surface of the dipping portion (4) exhibits an effect as an opening agent for the parison (8). The parison (8) is reheated by warm water to a temperature suitable for stretching. The warm water adhering to the outside of the parison (8) is extruded by the 2 nd pinch roll (9). A stretched film is obtained by injecting air into a tubular parison (8) heated to an appropriate temperature to form a bubble (10). Thereafter, the stretched film is folded by a 3 rd pinch roll (11) to form a double-layer film (12). The double-layer film (12) is wound up by a winding roll (13). The film is further cut and wound while being peeled off into one sheet, and is temporarily stored in a large roll for 1 to 3 days. Finally, the wound body of the vinylidene chloride-based resin wrap film contained in the packaging box is obtained by rewinding the wound body onto a paper core from a large roll and packing the wound body into the packaging box.

The steps from the 1 st pinch roll (7) to the 3 rd pinch roll (11) described above are stretching steps, the stretching magnification in the MD direction is determined by the rotation speed ratio of the 1 st pinch roll (7) to the 3 rd pinch roll (11), and the stretching magnification in the TD direction can be adjusted by the stretching temperature of the parison (8) and the size of the bubble (10).

On the other hand, the vinylidene chloride-based resin wrap film in which the ratio of low-mobility components measured by pulse NMR is controlled to 60% or more and which does not collapse even when the food wrapped therein is heated in a microwave oven can be suitably produced by setting the stretching ratio in MD to 4 to 9 times and the stretching ratio in TD to 2 to 6 times at a stretching temperature of 10 to 28 ℃.

Here, the MD direction is a film flow direction and refers to a direction in which the wrap is drawn out from the roll after the wrap is produced, and the TD direction is a direction perpendicular to the MD direction and refers to a direction perpendicular to a direction in which the wrap is drawn out from the roll after the wrap is produced.

The stretching ratio in the MD direction is a stretching ratio at which the parison (8) is stretched in the MD direction, and can be calculated from the ratio of the rotation speed of the 3 rd pinch roll (11) to the rotation speed of the 1 st pinch roll (7) in fig. 1, for example. The TD stretching ratio is a stretching ratio for stretching the parison (8) in the TD direction, and can be calculated from a ratio of the width of the two-layer film (12) to the width of the parison (8), for example, in fig. 1.

The cut large roll is not particularly limited after storage, and is, for example, rewound on a paper core or the like, and stored in a package case (14) provided with a film cutting blade (15) as shown in fig. 2 in the form of a wound body (16). As illustrated in fig. 2, the wrap film (17) is drawn out for use at the time of use.

[ examples ]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples. The measurement method and evaluation method of each physical property in examples and comparative examples are as follows.

(measurement method)

1. Content of vinylidene chloride repeating units

The ratio of vinylidene chloride repeating units in the vinylidene chloride-based resin wrap film was measured using a high-resolution proton nuclear magnetic resonance measuring apparatus (H-NMR: 400MHz or more). 0.5g of wrap film was dissolved in 10ml of tetrahydrofuran, and about 30ml of methanol was added to precipitate a resin component, and then the precipitate was separated by centrifugation and dried to obtain a reprecipitated filtrate. The reprecipitated filtrate was vacuum-dried, dissolved in deuterated tetrahydrofuran at 5% by weight, and the resulting solution was subjected to H-NMR measurement at a measurement atmosphere temperature of about 27 ℃. The vinylidene chloride repeating unit content of the copolymer of vinylidene chloride and vinyl chloride is calculated from peaks at 3.50 to 4.20ppm, 2.80 to 3.50ppm and 2.00 to 2.80ppm of the copolymer based on tetramethylsilane.

2. Thickness of the film

The measurement was carried out using a dial thickness gauge (TecLock Co., ltd.) in an atmosphere of 23 ℃ and 50% RH.

3. Tear strength

Assuming distribution of the wrap after shipment and storage at home, the tear strength of the wrap was measured after the wrap was stored for 1 month in a thermostatic bath set at 28 ℃. In the measurement, the tear strength was measured in an atmosphere of 23 ℃ and 50% RH using a light load tear tester type D (Toyo essence mechanism). The sample length in the tearing direction was set to 63.5mm, and the sample width was set to 50.0mm. In the measurement, the pendulum was lifted and stopped, and then the test piece was carefully attached to the jig, and the chuck was firmly fastened so that the position where the notch was cut was the center of the film width. The film was then scored with a cut using a knife mounted in the apparatus, and the pendulum was carefully released to read the amount of force required to tear the test piece. The test was conducted by excluding the test in which the tear line was not less than 10mm from the extension line of the cut mark and replacing the test with an additional test piece. For the measurement results, the value of the second digit after the decimal point is rounded.

4. Low temperature crystallization onset temperature

Assuming distribution of the wrap film after shipment and storage at home, the wrap film after production was stored in a constant temperature bath set at 28 ℃ for 1 month, and then the low-temperature crystallization starting temperature of the wrap film was measured. A Differential Scanning Calorimetry (DSC) apparatus (power-compensated dual-furnace DSC 8500) manufactured by Perkin Elmer was used, and a step-by-step scanning measurement mode (sample weight: 6mg, sample pan material: aluminum, measurement temperature: 0 to 180 ℃, temperature rise rate: 10 ℃/min, temperature rise step width: 4 ℃, isothermal time: 1 min) was used. The empty aluminum sample pan was also measured under the same temperature conditions and was used as a blank. The temperature at which heat release due to low-temperature crystallization starts out of the irreversible component of the temperature-heat flow curve is set as the low-temperature crystallization start temperature.

5. Pulse NMR

Assuming distribution of the wrap after shipment and storage at home, the pulse NMR of the wrap was measured after the wrap was stored in a thermostatic bath set at 28 ℃ for 1 month. The cut and approximately square preservative film 1g was folded and gathered into a cylindrical shape, and the cylindrical shape was filled in an NMR tube having a diameter of 10mm, and the measurement was carried out by the following conditions using pulse NMR.

[ Condition ]

The device comprises the following steps: m ini spec M Q20 manufactured by Bruker Bi & spin

Nuclide: 1H

And (3) determination: t2

The determination method comprises the following steps: solid echo method

Measuring temperature: 40 deg.C (measuring after 5min to reach the set temperature)

Cumulative number of times: 256 times

Repetition time: 1.0 second

Sample amount: about 1g

The obtained Free Induction Decay (FID) curve was separated into 3 components using the following formula, and the component ratio and relaxation time were determined for each component.

A component represented by a combined function of a Gaussian function and a sinc function of a first term of the following expression is set as a low-mobility component, a component represented by a Lorentz function of a second term of the following expression is set as an intermediate component, and a component represented by a Lorentz function of a third term of the following expression is set as a high-mobility component.

[ formula 2]

C _s : mole fraction of low motility component

C _m : mole fraction of intermediate component

C _l : mole fraction of highly motile ingredient

T _s : relaxation time of low mobility component

T _m : relaxation time of intermediate component

T _l : relaxation time of high mobility component

6. Method for preparing cooked rice

Cooked rice was produced by the following steps (1) to (3).

(1) Cooking: 600g of Yuanguang disposable rice produced in Sanxian province was cooked with 798g of tap water (1.33 times of the weight of disposable rice) by means of the disposable rice program of IH rice cooker (like printing).

(2) Packaging: after cooking rice by the method (1), the rice in the pot is fully and uniformly stirred by a rice spoon, and 150g of the rice is held by a hand to be shaped into balls.

(3) And (3) natural cooling: the molded cooked rice was naturally cooled at room temperature (23 ℃) until the surface temperature reached 40 ℃, and then left in a refrigerator for 24 hours until the surface temperature reached 5 ℃.

(4) Evaluation of ease of wrapping: the cooked rice obtained in (3) was packaged with a wrap film, and the ease of wrapping at this time was judged by 4 grades of 3 points (easy wrapping), 2 points (easy wrapping), 1 point (slightly difficult wrapping), and 0 point (difficult wrapping). The evaluation was performed on the following 4 grades using an average score of 30 critics.

(5) Evaluation of non-collapsibility: the rice wrapped with the wrap was heated in a 800W microwave oven for 5 minutes together with the wrap, and the degree of collapse of the rice after the heating was visually confirmed, and the degree of collapse at that time was judged by 4 grades of 3 cents (almost no collapse), 2 cents (extremely slight collapse), 1 cents (slight collapse), and 0 cents (collapse).

The evaluation was performed on the following 4 grades using an average score of 30 critics.

[ example 1]

Vinylidene chloride resin having a weight average molecular weight of 90,000 (vinylidene chloride repeating unit: 85% and vinyl chloride repeating unit: 15%), ATBC (tributyl acetylcitrate, taokang chemical Co., ltd.), ESO (Newcizer 510R, nippon fat and oil Co., ltd.) were mixed in proportions of 93.4 wt%, 5.5 wt%, and 1.1 wt%, and the total of 10kg of the mixture was mixed in a Henschel mixer for 5 minutes and aged for 24 hours or more to obtain a vinylidene chloride resin composition.

The vinylidene chloride resin composition was fed to a melt extruder and melted, and the melt resin was extruded into a ring shape at an extrusion rate of 10kg/hr while adjusting the heating conditions of the extruder so that the temperature of the melt resin at the slit outlet of the ring die attached to the tip of the extruder became 170 ℃. The inner diameter of the die gap is set to be 50mm.

After the film was supercooled, the MD direction was stretched 7.4 times and the TD direction was stretched 2.5 times at a stretching temperature of 25 ℃ to form a cylindrical film, and 2 overlapped films of 125mm in width of the two-layer film were wound at a winding speed of 18 m/min. The film was cut into 115mm wide pieces, and the pieces were rewound on a paper core having an outer diameter of 92mm while being peeled into 1 sheet. Then, the film was stored at 15 ℃ for 30 hours, and wound on a paper core having an outer diameter of 36mm and a length of 300mm for 20m, thereby obtaining a wound body of wrap film. The evaluation results are shown in table 1.

[ example 2]

A roll of cling film was obtained in the same manner as in [ example 1] except that extrusion was performed at an extrusion rate of 12.5kg/hr, and the TD direction was extended to 3.5 times the width of the double film to 178 mm. The evaluation results are shown in table 1.

[ example 3]

A roll of cling film was obtained in the same manner as example 1, except that extrusion was performed at an extrusion rate of 15kg/hr, and the TD direction was extended to 4.3 times the width of the double-layer film to 215 mm. The evaluation results are shown in table 1.

[ example 4]

A roll of cling film was obtained in the same manner as in example 1, except that extrusion was performed at an extrusion rate of 18kg/hr, and the TD direction was extended to 4.7 times to make the width of the double film 235 mm. The evaluation results are shown in table 1.

[ example 5]

A roll of wrap film was obtained in the same manner as in example 1 except that the rolled wrap film was stretched at 20 ℃ in the TD direction by a factor of 2.5. The evaluation results are shown in table 1.

[ example 6]

A roll of wrap film was obtained in the same manner as in example 1 except that the rolled wrap film was stretched at 15 ℃ in the TD direction by a factor of 2.4. The evaluation results are shown in table 1.

[ example 7]

A roll of a plastic wrap was obtained in the same manner as in example 1, except that a vinylidene chloride resin having 71% vinylidene chloride repeating units and 29% vinyl chloride repeating units was used, extrusion was performed at an extrusion rate of 20kg/hr, and the TD direction was extended by 5.5 times to make the width of the double-layer film 275 mm. The evaluation results are shown in table 1.

[ example 8]

A roll of a wrap film was obtained in the same manner as in example 1 except that a vinylidene chloride resin having a vinylidene chloride repeating unit of 73% and a vinyl chloride repeating unit of 27% was extruded at an extrusion rate of 15kg/hr, and the TD direction was extended by 4.3 times to make the width of the double layer film 215 mm. The evaluation results are shown in table 1.

[ example 9]

A roll of wrap film was obtained in the same manner as in example 1 except that a vinylidene chloride resin having 78% of vinylidene chloride repeating units and 22% of vinyl chloride repeating units was extruded at an extrusion rate of 15kg/hr, and the TD direction was extended by 4.3 times to make the width of the double-layer film 215 mm. The evaluation results are shown in table 1.

[ example 10]

A roll of wrap film was obtained in the same manner as in example 1 except that a vinylidene chloride resin having 88% of vinylidene chloride repeating units and 12% of vinyl chloride repeating units was extruded at an extrusion rate of 15kg/hr, and the TD direction was extended by 4.3 times to make the width of the double-layer film 215 mm. The evaluation results are shown in table 2.

[ example 11]

A roll of wrap film was obtained in the same manner as in example 1 except that a vinylidene chloride resin having a vinylidene chloride repeating unit of 92% and a vinyl chloride repeating unit of 8% was extruded at an extrusion rate of 15kg/hr, and the TD direction was extended by 4.3 times to make the width of the double layer film 215 mm. The evaluation results are shown in table 2.

[ example 12]

A roll of wrap film was obtained in the same manner as in example 1, except that a vinylidene chloride resin having a vinylidene chloride repeating unit of 94% and a vinyl chloride repeating unit of 6% was used and the TD direction was extended by 2.5 times. The evaluation results are shown in table 2.

[ example 13]

A roll of cling film was obtained in the same manner as in example 1, except that a mixture of 98.5 wt% vinylidene chloride resin, 0.5 wt% ATBC, and 1.0 wt% ESO was used. The evaluation results are shown in table 2.

[ example 14]

A roll of wrap film was obtained in the same manner as in example 1, except that a mixture of 97.5 wt% vinylidene chloride resin, 1.2 wt% ATBC, and 1.3 wt% ESO was used. The evaluation results are shown in table 2.

[ example 15]

A roll of wrap film was obtained in the same manner as in example 1 except that a mixture of 96 wt% of vinylidene chloride resin, 1.0 wt% of ATBC, 1.7 wt% of DALG (diacetylated glycerol monolaurate, physically ground vitamin) and 1.3 wt% of ESO was used. The evaluation results are shown in table 2.

[ example 16]

A roll of a cling film was obtained in the same manner as in example 1, except that a mixture of 94 wt% of a vinylidene chloride resin, 3 wt% of DBS (dibutyl sebacate, daoctal chemical industry), 1.7 wt% of DALG, and 1.3 wt% of ESO was extruded at an extrusion rate of 12.5kg/hr, and the TD direction was extended 3.5 times to make the width of the double film 175 mm. The evaluation results are shown in table 2.

[ example 17]

A roll of a cling film was obtained in the same manner as in example 1, except that a mixture of 93.4 wt% vinylidene chloride resin, 5.3 wt% ATBC, and 1.3 wt% ESO was extruded at an extrusion rate of 20kg/hr, and the TD direction was extended 3.5 times to make the width of the double film 280 mm. The evaluation results are shown in table 2.

[ example 18]

A roll of a cling film was obtained in the same manner as in example 1, except that a mixture of 92.5 wt% vinylidene chloride resin, 3.0 wt% ATBC, 2.5 wt% DALG, and 2.0 wt% ESO was extruded at an extrusion rate of 20kg/hr, and the TD direction was extended 4.3 times to make the width of the double film 280 mm. The evaluation results are shown in table 2.

[ example 19]

A roll of a plastic wrap was obtained in the same manner as in example 1 except that a mixture of 91.5 wt% of a vinylidene chloride resin, 2.5 wt% of ATBC, 2.0 wt% of DALG, 2.0 wt% of DBS and 2.0 wt% of ESO was extruded at an extrusion rate of 20kg/hr, and the TD direction was extended by 4.3 times to make the width of the double-layer film 280 mm. The evaluation results are shown in table 2.

[ example 20]

A roll of cling film was obtained in the same manner as in example 1, except that the inner diameter of the die gap was set to 30mm, extrusion was performed at an extrusion rate of 6kg/hr, the width of the double film was set to 76mm, and slitting was performed at a width of 65 mm. The evaluation results are shown in table 2.

[ example 21]

A roll of cling film was obtained in the same manner as in example 1, except that the inner diameter of the die gap was set to 35mm, extrusion was performed at an extrusion rate of 7kg/hr, the width of the double film was set to 88mm, and slitting was performed at a width of 80 mm. The evaluation results are shown in table 3.

[ example 22]

A roll of cling film was obtained in the same manner as in example 1, except that the inside diameter of the die gap was set to 40mm, extrusion was performed at an extrusion rate of 8kg/hr, the width of the double film was set to 100mm, and cutting was performed at a width of 90 mm. The evaluation results are shown in table 3.

[ example 23]

A roll of cling film was obtained in the same manner as in example 1 except that the inner diameter of the die gap was set to 45mm, extrusion was performed at an extrusion rate of 9kg/hr, the width of the double film was set to 113mm, and slitting was performed at a width of 100 mm. The evaluation results are shown in table 3.

Comparative example 1

A roll of cling film was obtained in the same manner as in example 1, except that extrusion was performed at an extrusion rate of 20kg/hr, the MD direction was 3.7 times and the TD direction was 5.6 times, and the width of the double film was 280 mm. The evaluation results are shown in table 3.

Comparative example 2

A wrap of a cling film was obtained in the same manner as in example 1 except that a vinylidene chloride resin having a weight average molecular weight of 110,000, a vinylidene chloride resin having a vinylidene chloride repeating unit of 84% and a vinyl chloride repeating unit of 16% was used, the vinylidene chloride resin was extruded at an extrusion rate of 15kg/hr with an addition amount of ATBC of 2.3%, an addition amount of ESO of 2.2%, and an addition amount of DALG of 2.8%, the MD direction was stretched 4.2 times, the TD direction was stretched 4.3 times, and the width of the two-layer film was 215 mm. The evaluation results are shown in table 3.

Comparative example 3

A roll of cling film was produced in the same manner as in example 1 except that the vinylidene chloride resin had a weight average molecular weight of 130,000, 80% vinylidene chloride repeating units and 20% vinyl chloride repeating units, 5.2% ATBC and 1.8% ESO were added, and the double-layer film was stretched at a stretch ratio in MD of 4.5 times and a stretch ratio in TD of 3.6 times at an extrusion rate of 12.5kg/hr to give a roll of cling film. The evaluation results are shown in table 3.

Comparative example 4

A roll of a cling film was produced in the same manner as in example 1 except that the vinylidene chloride resin had a weight average molecular weight of 130,000, the vinylidene chloride repeating units were 81%, the vinyl chloride repeating units were 19%, the ATBC was 5.3% by weight, the ESO was 1.5% by weight, the extrusion rate was 12kg/hr, the double-layer film was stretched at a stretch ratio in MD of 4.9 times and a stretch ratio in TD of 3.1 times to obtain a 157mm width, and a roll of the cling film was obtained. The evaluation results are shown in table 3.

Comparative example 5

A wrap of cling film was obtained in the same manner as in example 1, except that the stretching temperature was 30 ℃. The evaluation results are shown in table 3.

Comparative example 6

A roll of cling film was produced in the same manner as in example 1, except that a vinylidene chloride resin having 71% vinylidene chloride repeating units and 29% vinyl chloride repeating units was used, and extrusion was performed at an extrusion rate of 15kg/hr to obtain a double-layer film having a width of 215 mm. The evaluation results are shown in table 3.

Comparative example 7

A film was produced in the same manner as in example 1, except that a vinylidene chloride resin having 94% of vinylidene chloride repeating units and 6% of vinyl chloride repeating units was extruded at an extrusion rate of 15kg/hr and the TD direction was extended 4.3 times, but a film could not be formed under these conditions.

[ Table 1]

[ Table 2]

[ Table 3]

Claims

1. A vinylidene chloride resin wrap film comprising a vinylidene chloride resin in an amount of 89% by weight or more, wherein the low-mobility component ratio measured by pulse NMR is 60% or more, the low-temperature crystallization onset temperature of the vinylidene chloride resin measured by a temperature modulation differential scanning calorimeter is 60 ℃ or more, and the vinylidene chloride resin contains a vinylidene chloride repeating unit in an amount of 72 to 93%.

2. The vinylidene chloride-based resin preservative film according to claim 1, wherein the vinylidene chloride-based resin contains at least one additive selected from the group consisting of citric acid esters, dibasic acid esters, acetylated fatty acid glycerides, and epoxidized vegetable oils in a total amount of 2 to 8% by weight.